Early Results: A First-Ever Malaria Vaccine Protects Children

A first-ever malaria vaccine tested in children in sub-Saharan Africa cut the risk of infection with malaria by about half, researchers announced in a teleconference on Tuesday.

Scientists working in a public-private partnership involving GlaxoSmithKline (GSK) Biologicals, the PATH Malaria Vaccine Initiative and the Bill and Melinda Gates Foundation, at 11 sites in Africa, reported that the experimental vaccine known as RTS,S was 56% effective in protecting children aged 5 to 17 months from infection with malaria a year after immunization. The vaccine was also 47% effective in preventing severe cases of the disease. The results of the late-stage trial were published online by the New England Journal of Medicine.

“This vaccine shows an important impact in terms of protection against clinical and severe malaria,” Christian Loucq, director of the PATH Malaria Vaccine Initiative, tells TIME, noting that among the first 6,000 children who received the vaccine (or a control vaccine), researchers saw 1,500 cases of clinical malaria among those in the control group, compared with only 750 cases — or half — among those receiving the malaria vaccine.

The trial is not complete. The researchers are continuing to gather data on a younger group of infants, aged 6 to 12 weeks, who are being vaccinated as well. This group would be the target population for the malaria vaccine, should it prove effective, since they take part in routine public health inoculation programs. Both age groups will be followed for nearly three years to track malaria infections and to see how long protection lasts; researchers are also collecting additional safety data in infants. The trial, which involves a total of 15,460 children, will be completed in 2014.

The next question the scientists hope to answer is whether an efficacy of around 50%, as the current trial shows, is good enough to start vaccinating youngsters in countries where malaria is endemic. In sub-Saharan Africa, the mosquito-borne disease infects millions each year and kills 800,000 youngsters annually. But other vaccines that children receive against childhood infections, such as measles and rotavirus, reach efficacy rates of 70% to more than 90%.

At its current power, the candidate vaccine “potentially translates to tens of millions of malaria cases among children that can be averted annually,” Dr. Tsiri Agbenyega, head of the malaria research unit at the Komfo-Anokye Hospital in Ghana and chair of the RTS,S Clinical Trials Partnership Committee, told reporters during Tuesday’s briefing. “The study found that RTS,S also reduced risk of severe malaria by 47%. That’s remarkable when you consider that there has never been a successful vaccine against a human parasite, nor against malaria.”

Still, says Dr. Regina Rabinovich, director for infectious diseases of the global health program at the Bill & Melinda Gates Foundation, “Would I prefer to see a 100% effective vaccine? Absolutely.”

Whether or not a malaria vaccine can achieve that level of effectiveness isn’t clear. The development team is confident that the percentage may improve as the RTS,S trials continue, particularly in younger children. In addition, the trial is also testing whether children vaccinated with all three doses of the vaccine, plus a booster 18 months later, are better protected than children receiving just the malaria doses alone.